Permethrin, a broad-spectrum insecticide useful against a variety of pests on nut, fruit, vegetable, cotton, ornamental, mushroom, potato, and cereal crops. Permethrin is a synthetic pyrethroid which exhibits repellent as well as knockdown and kill activity against insects. Pyrethroids, including both the naturally-occurring compounds and their synthetically prepared analogs effectively control a variety of pests, such as ticks, cockroaches, houseflies, mosquitoes, black flies, fleas, and other flying or crawling insects. Pyrethroids are not harmful to plants, food, animals or humans, and leave no harmful residues. Permethrin has also been applied on fabric to help combat mosquitoes, ticks, fleas, bedbugs, chiggers, and flies.
Fabrics coated with active agents, and in particular insecticidal agents, are known in the patent literature, as well as compositions and methods for preparing such treated textiles. These fabrics have beneficial utility when sewn into an article of manufacture such as a tent, tarpaulins, sleeping bag, and protective outerwear garments for both civilian and military applications. For example, U.S. Pat. Nos. 3,859,121 (Yeadon et al), 4,765,982 (Ronning et al), 5,089,298 (McNally et al), 5,198,287 (Samson et al), 5,252,387 (Samson et al), 5,503,918 (Samson et al), 5,631,072 (Samson et al), 6,015,570 (Tucci et al), 6,030,697 (Samson et al), and 6,440,438 (Platts) all pertain to textile fabrics that have been treated with an insect repellent.
A major concern of using permethrin as an insect repellent in treated fabrics resides in the wash durability of the insecticide. That is, the retention of permethrin in garments made from treated fabric through repeated wash cycles during machine laundering. It is to this aspect of insecticidally-treated textiles that the present invention pertains.
For example, U.S. Pat. No. 5,089,298 discloses a synergism between an amylopectin (a water soluble form of starch)-permethrin combination on textile fabrics to afford greater retention of permethrin in clothing through repeated wash cycles as compared to garments treated only with permethrin. Another example is disclosed in U.S. Pat. No. 5,503,918 wherein the addition of polyvinyl acetate as a binder for the permethrin dispersion preserves the effectiveness of the permethrin through more washings of the fabric than does the amylopectin used in the '298 patent. U.S. Pat. No. 5,631,072 discloses wash durable permethrin-treated garments prepared from a fabric that is either impregnated or single-side surface-coated with a dispersion of permethrin. In the case of impregnation, a dispersion of permethrin, a polymeric binder such as acrylic copolymer or polyvinylacetate, and optionally a cross-linking agent (e.g., methylated melamine resin), are used. In the single-side surface coating embodiment, the fabric is treated with the insecticide and a thickener (e.g., carboxymethylcellulose), and optionally a polymeric binder that is optionally cross-linked.
Additional patents focusing on one or both of incorporation and retention of either permethrin or a pyrethroid on fabric are as follows:
U.S. Pat. No. 3,859,121 teaches methods for retarding insect repellent contamination of foodstuffs stored in contact with cellulosic textile that has been treated with such repellent, by incorporating into the impregnation composition an antimigrating agent. An insecticidal combination of pyrethrin and piperonyl butoxide are impregnated in association with an emulsifing polyoxyethylene sorbitol ester of a mixed C12 fatty acid, a hydroxyalkyl cellulose thickener, and an antimigrating agent such as water soluble polyalkylene glycol, polypropylene triol or pentol of specified average molecular weight, corn oil, tung oil, linseed oil, linoleic acid dimer or trimer, and others.
U.S. Pat. No. 4,765,982 discloses controlled release insect control devices (e.g., webs, tapes, sheets, pads) based on microencapsulated pyrethroid insecticide that self-adheres to rough-surfaced fibers comprised of graft polymers of cellulose and an ethylenically unsaturated material copolymerizable therewith.
U.S. Pat. No. 6,030,697 discloses a method for impregnating BDU's (battle dress uniforms), made from conventional (e.g., untreated twill) fabric with permethrin by adding an aqueous solution (approximately 1%) of permethrin to the wash cycle of an industrial washing machine, and returning all extracted and spin waters containing permethrin to a holding tank for subsequent reuse.
U.S. Pat. No. 5,198,287 discloses a tent fabric with a water repellent and flame retardant coating that includes the insecticide permethrin. The patent focuses on the oxygen- and light-sensitivity of permethrin. According to the '287 invention, permethrin is incorporated in the coating on the inner surface of the tent fabric to shield the permethrin from oxygen and ultraviolet light, thereby providing an effective life of more than six months for the permethrin. Similarly, U.S. Pat. No. 5,252,387 also deals with the oxygen- and light-sensitivity of permethrin in insect repellent fabric and discloses that permethrin can be preserved in the fabric by placing a barrier layer over the permethrin to protect the permethrin from degradation by ultraviolet light and oxygen.
The use of binders in coating “actives” on textiles is widely known in the literature and practiced in the textile industry. More specifically, polymer binders are utilized to aid in improving adhesion and abrasion resistance of the “active” (e.g., a flame retardant, a water repellant, an insect repellant.) U.S. Pat. Nos. 4,594,286 and 4,833,006 are examples of flame resistant, water repellant woven fabrics using blocked polyester/polyether urethane prepolymer or polyfunctional (unblocked) isocyanate, respectively, as binders to aid in the retention of coated “active”.
U.S. Pat. Nos. 5,300,192, 5,447,977, 5,571,618, 5,609,727, and 5,611,885 are all commonly assigned to Weyerhaeuser Co. and pertain to the use of reactivatable binders for binding particles to fibers, particularly wet laid or high bulk fibers for web or sheet production, either cellulosic (wood pulp) or synthetic in nature. These patents disclose both polymeric and non-polymeric organic binders having multiple functionalities which, via a combination of hydrogen bonding and coordinate covalent bonding, bind to both the fiber substrate and the particulate to be adhered. Both the fiber and the particulate are functionally reactive with the binder. Examples of polymeric binders include PEG, PPG, polyacrylic acid, polyamides, polyamines, polyaldehydes, and poly(caprolactone) diol. Examples of non-polymeric binders include glycerin, ascorbic acid, urea, glycine, pentaerythritol, a monosaccharide, a disaccharide, citric acid, tartaric acid, dipropylene glycol, and DMDHEU. The binders of the Weyerhaeuser patents have reactivatable funtionality, allowing, e.g., the binder to be adhered to the fiber at one point in production and at a later point in time the functionality for binding the particulate is activated to bind the particulate. While the preferred particles for adhering to the fibrous products or high bulk fibers of most of these patents are superabsorbent particles and/or antimicrobials (e.g., to produce a diaper or other absorbent hygiene product), these patents disclose a long and diverse laundry list of particulates that can be bound to the fibrous products, including, e.g., certain insecticides. (Table I). Permethrin, however, is not recited. Additionally, while the nature of the bonding (i.e., either H-bond or coordinate covalent bond) of the particles to the binder affords the particles to stay in contact with the fibers and resist dislodgement therefrom by mechanical forces applied to the endproduct (a fibrous mat) during manufacture, storage or use, the fibrous products to which these patents pertain are not intended to be laundered, either once or repeatedly. Hence the Weyerhaeuser disclosures do not appreciate the challenges posed by improving the wash durability of garments made from permethrin-treated woven textiles.